Malaria, dengue, and West Nile Fever are currently the most mentioned mosquito-borne diseases affecting humans. An estimated 1.2 billion clinical attacks of malaria occur each year in Africa. According to the latest consensus of scientists and health workers, malaria kills up to 2.7 million persons each year. Ninety percent of these cases and deaths occur in Africa, and a large portion of them involve children under the age of five. Approximately 1.7 million African children die yearly due to malaria-linked illnesses. Meanwhile, it is estimated that about 50-100 million dengue fever cases occur annually, including a few hundred thousand cases of the life-threatening form (dengue hemorrhagic fever).
Transmission of mosquito-borne diseases occurs through inoculation whereby infected blood-feeding mosquitoes bite target organisms, such as humans, and transfer the disease pathogen into the target's bloodstream. A variety of mosquito species, including Aedes aegypti (dengue, yellow fever), Anopheles quadrimaculatus (malaria), Culex quinquefasciatus (West Nile virus) and Cx. pipiens (West Nile virus) are vectors of blood-borne pathogens that cause disease in humans and other mammals. For example, dengue, yellow fever are transmitted by Aedes aegypti, malaria is transmitted by Anopheles quadrimaculatus (malaria), and West Nile virus is transmitted by Cx. quinquefasciatus and Cx. Pipiens. 
Control of insect pests such as mosquitoes is achieved using a variety insecticidal materials. Some insecticidal materials include proteins that are made by the bacterium Bacillus thuringiensis. Bacillus thuringiensis (Bt) is a ubiquitous facultative anaerobic, Gram-positive, motile, spore-forming bacterium that produces proteins that accumulate as crystals within the bacterial cell. These insecticidal crystal proteins are toxic to a number of insects, mainly insects in the orders Coleoptera, Diptera, and Lepidoptera. Pesticidal formulations containing Bt crystal proteins have been used extensively in commercial agriculture, forest management, and mosquito control. Bt is a member of the B. cereus (Bc) group that includes B. cereus, B. anthracis, and B. mycoides. Bt has been classified according to its cellular, cultural, biochemical, and genetic characteristics. However, serotypic and specific biochemical characteristics have been found to be inconsistent. Bt can only be differentiated from Bc by the production of one or more of the insecticidal crystalline (Cry) proteins that are toxic to invertebrates.
Bt is accepted as a source of environment-friendly biopesticide. Farmers have applied Bt as an insecticidal spray for control of lepidopteran and coleopteran pests for more than 30 years. The United States Environmental Protection Agency has considered Bt sprays to be so safe that it has exempted them from the requirement of a tolerance (a standard for a maximum permissible residue limit on food).
The mechanism of action of the Bt crystal proteins involves solubilization of the crystal in the insect midgut to yield a solubilized prototoxin, proteolytic processing of the prototoxin by midgut proteases to yield a Cry toxin, binding of the processed Cry toxin to midgut receptors, and insertion of the Cry toxin into the apical membrane to create ion channels or pores. The introduction of channels or pores permits the free flow of fluids into the cells, which eventually leads to bursting of the cells and death of the insect.
Of the many known Cry proteins, most have limited range of toxicity against insects, and are often quite specific for only one or a few insect genera. Importantly, the known Cry proteins exhibit only limited toxicity to the range of mosquito genera that are responsible for disease in humans and other mammals. Accordingly, it would be desirable to provide Bt Cry proteins that have enhanced toxicity to insects, and more particularly to one or more genera of mosquitoes that are associated with human disease.